This invention relates to a method and a device for detecting when the driver of a motor vehicle becomes tired while the vehicle is operating.
Japanese document JP 07 093 678 A discloses a method for detecting tiredness of the driver of a vehicle, in which a steering action that follows a steering inactivity phase is sought.
U.S. Pat. No. 4,594,583 discloses a method for detecting tiredness and for warning drivers in which a steering inactivity phase and a subsequent steering action are detected, and the driver is subsequently warned. This warning can be suppressed through the observation of a further vehicle operating parameter.
The object of the invention is to provide a method and a device which ensure reliable detection of the tiredness of a driver of a vehicle.
This object is achieved by means of the features of the invention claimed.
The method according to the invention detects tiredness of the driver of the vehicle when a steering inactivity phase and a subsequent steering action are detected. The implementation of the steering inactivity phase is logically combined with the steering action. For this purpose, the movement of a steering wheel of the vehicle is sensed in the form of the steering wheel angle x. A sensor for sensing the steering wheel angle is usually present in any case in modern vehicles. A steering inactivity phase is sensed when the steering wheel angle remains within a steering wheel angle interval ΔX during a predetermined time interval. The subsequent steering action and the magnitude of the implementation of the steering action are sensed in the form of the maximum gradient of the steering wheel angle, that is to say for example the steering wheel angle speed, which occurs then. Tiredness of the driver is advantageously detected only if the steering wheel angle remains within the predetermined steering wheel angle interval during a specific time period and the time period exceeds a predetermined threshold value and at the same time a steering wheel action which is sensed after this exceeds a predetermined value of the maximum steering wheel angle gradient in terms of its implementation.
At times Ti, the implementation of the steering inactivity phase is logically combined with the implementation of the steering action, stored, and provided with a weighting factor, which is also stored. This logic combination and storage, together with weighting factors, are carried out repeatedly so that the logic combination and storage and weighting take place at the various times Ti during a time interval. In each case, a mathematical mean value of the stored values is formed at the times Ti at the end of a further time interval. In this context, an arithmetical mean value is preferably formed.
The inclusion of what are referred to as secondary factors in the weighting factor is particularly advantageous. A steering situation is determined for this purpose. In order to acquire a steering situation at the times Ti, a classification of the steering situations is carried out by means of data from a plurality of sensors in the vehicle and/or by means of data relating to operator control interventions in the vehicle. It is particularly advantageous here that the data which is used from the plurality of sensors in the vehicle and/or the data relating to operator control interventions in the vehicle is usually present in any case in an accessible form on the data bus in modern vehicles. The classification of the steering situation makes it possible to divide the steering situations into a plurality of classes which characterize the type of the steering situation in more detail. It is, for example, particularly advantageous to provide, in the classification of the steering situation, a tiredness-induced steering situation, a distraction-induced steering situation, and an environment-induced steering situation. The weighting factor in distraction-induced steering situations and in environment-induced steering situations is advantageously lower here than in tiredness-induced steering situations.
This provides the advantage that assignment of a steering action to a tiredness-induced steering action is improved. Steering events are in fact always gated out or weighted less strongly if it is proven to a conditional degree by the steering situation that it is distraction-induced or environment-induced.
Distraction-induced steering events occur, for example, if, in a time interval around the steering event, the flashing indicator light, the cruise controller lever, the headlights, the horn, the wiper, the voice-control lever, the steering wheel pushbutton keys, the steering column adjustment, the operator control unit, the air-conditioning system or the like is activated. Steering events which occur in the steering situation are then either completely gated out or weighted less strongly. The classification of the steering situations permits weighting according to the severity of the distraction. In a similar way it is possible to detect an environment-induced steering situation. Side wind, aquaplaning, the limiting range of the vehicle movement dynamics or the like can force the driver to carry out steering maneuvers which could initially be assigned to patterns of tired or inattentive drivers. Here, the detection of the environment-induced steering situation is important. In order to detect such a steering situation it is possible to have recourse to further vehicle sensors.
It is particularly advantageous to provide a further gradation of the weighting, corresponding to the severity of the distraction, within one class of steering situations. For example, the adjustment of the volume of the radio is to be given a less strong weighting than the inputting of a navigation destination.
Through the weighting and, if appropriate, the exclusion of individual steering maneuvers, the invention permits more reliable detection of tiredness or inattentiveness and permits incorrect events to be eliminated. Both the detection of inattentiveness and the detection of tiredness are improved. In particular, steering actions which are induced by the outside are eliminated. The elimination and weighting of operator control actions enable tiredness events to be separated from inattentiveness events. This permits both tiredness and inattentiveness to be detected.
The abovementioned object of the invention is also achieved by means of a control unit for carrying out the described method. The advantages of this solution correspond to the advantages mentioned with respect to the described method.